Humans, livestock and rat monocrotaline (MCT) pneumotoxicity is associated with a spectrum of pulmonary vascular lesions reminiscent of idiopathic pulmonary hypertension in humans. A feature common to all forms of pulmonary hypertension and vascular diseases in the initial insult/injury that leads to pathogenic progressive vascular remodeling. The proposed research addresses the applicant's working hypothesis that ornithine decarboxylase (ODC) regulation is a central convergence point for the multiple signaling pathways driving vascular remodeling and angiogenesis. The investigator's studies have shown elevated ODC activity is essential for the progressive vascular thickening that underlies the development of monocrotaline (MCT)-induced pulmonary hypertension. Although many signaling cascades are initiated by cytokines, growth factors and redox-active molecules in response to the injury and inflammation associated with MCT pneumotoxicity and other vascular diseases, the vascular remodeling response is likely due to interactions of intracellular signaling pathways and transcription factors. In this context, MCT activates transcription factors capable of binding a putative multi-functional "stress/injury" enhancer region in intron 1 of the ODC gene. The investigators postulate that c-myc is activated by MCT-generated stimuli and cooperatively interacts with other factors binding the "stress/injury" enhancer element in the ODC gene to enhance ODC transcription. A comprehensive approach employing rats, isolated pulmonary arteries and cultured endothelial cells will be used. Aim 1 will determine molecular mechanisms responsible for MCT-activated ODC gene transcription by testing the hypotheses that: MCT regulates ODC transcription by stimulating nuclear factors to activate the "stress/injury" enhancer element in ODC. Enhancer and promoter element functionality will be examined by direct in vivo and in vitro transfer of chimeric ODC/reporter gene constructs and studying their response to MCT. DNase 1 protection, gel mobility shift and methylation interference assays will identify specific regions and proteins. The second hypothesis will test if MCT causes altered patterns of expression of c-myc protein and mRNA in discrete lung cell types as a function of time and pathophysiological events. Aim 2 will determine if increased vascular ODC activity is not only required, but also sufficient by itself, to cause pulmonary vascular remodeling and angiogenesis by testing whether direct in vivo and in vitro transfer of ODC cDNA encoding sense or antisense RNA will increase or inhibit ODC activity sufficient to alter fibronectin, PCNA, polyamines, vascular structure and neovascularization in a manner similar to MCT, or if antisense will prevent these MCT-caused pathologies. How the seemingly diverse signals driving vascular remodeling are integrated into a final common pathway is a key question in biology. This research may point to ODC as an obligatory link in the integration of this pathway and thus in the vascular pathogenesis of many diseases, including cancer, atherosclerosis, restenosis after angioplasty, and hypertension.